COMPARATIVE EFFECTIVENESS OF INACTIVATED AND LIVE-ATTENUATED INFLUENZA VACCINE IN CHILDREN: A DECISION-ANALYTIC MODEL

Purpose: Current literature on the comparative effectiveness of live-attenuated influenza vaccine (LAIV) versus trivalent inactivated influenza vaccine (TIV) in children is conflicting; recommendations about which vaccine is more effective may differ based on hard-to-predict parameters, including vaccine effectiveness (VE) and attack rates (AR) of influenza that vary between seasons. We constructed a decision-analytic model assessing comparative effectiveness of TIV vs. LAIV for children in a given influenza season, in terms of quality-adjusted life years (QALYs) gained per children vaccinated.

Method: In this decision-analytic model, children face a risk of vaccine-related adverse events and reduced risk of influenza infection (described by VE). We assumed VE estimates of 43% (TIV, derived from meta-analytic estimates) and 46% (LAIV, derived from current estimates), and an influenza AR of 5% in base case scenarios. We varied each of these values in deterministic sensitivity analyses to determine whether the comparative effectiveness of TIV vs. LAIV varied according to AR in a hypothetical influenza season where H3N2 was the dominant circulating strain.

Result: In a given H3N2 influenza season with AR of 5%, vaccination with LAIV (compared to TIV) resulted in a gain of 1.69 QALYs per 100,000 children vaccinated. Sensitivity analyses varying the VE of both TIV and LAIV showed that TIV resulted in a gain in QALYs over LAIV only when TIV has a VE at least nine percentage points greater than LAIV, holding AR at 5%. Furthermore, assuming the base case VE for LAIV, TIV was found to yield a greater QALY gain compared to LAIV when attack rates were at 5% or greater and TIV VE was 55% or greater, or when attack rates were 7% or greater and TIV VE was 52% or greater.

Conclusion: At published VE estimates against H3N2 for TIV and LAIV, and assuming a high attack rate of H3N2 influenza, vaccinating children with LAIV is calculated to be more effective than TIV for optimizing QALYs in children. However, this difference in QALYs is relatively small, and with a positive relationship between difference in QALYs and influenza attack rate, the difference is even less for for seasons with a lower attack rate. In order to make robust conclusions about this relationship, further research should incorporate additional age groups and influenza types and subtypes.